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Title: Can peg strength be used as a predictor for pod maturity and peanut yield

item Sorensen, Ronald - Ron
item Lamb, Marshall
item Butts, Christopher - Chris

Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2015
Publication Date: 9/16/2015
Citation: Sorensen, R.B., Lamb, M.C., Butts, C.L. 2015. Can peg strength be used as a predictor for pod maturity and peanut yield? Peanut Science. 42(2):92-99. doi: 10.3146/0095-3679-42.2.92.

Interpretive Summary: Variability in phenotypic peg strength may contribute to increased yield or digging losses in some peanut cultivars. The indeterminate characteristic of peanut growth and pod maturity could confuse growers to determine best time to dig. Digging too early could increase the amount of immature peanuts that could increase possible risk of aflatoxin during storage and cause off flavors during roasting. Conversely, digging too late could reduce yield (increased digging loss) caused by mechanical or biological damage to the plant during digging or combining. Therefore, harvesting peanut at the proper time would have greatest yield, least pod loss, and reduce the risk for aflatoxin in the warehouse and food processor would have less risk of off flavors during roasting. All previous research has shown differences in peg strength versus peanut cultivar and peg strength tended to decrease with age especially after full maturity (black hulls). The advance of genetic enhancements associated with newer cultivars for increased yield, disease, and insect resistance may also have different peg strengths that could be used to determine pod maturity pod yield, and possibly digging date. It is unknown how new runner type cultivar peg strengths compare to each other and how variability in peg strength may affect the harvestable yield among cultivars. By using peg strength as a determinate of when to harvest along with mesocarp (hull) color, growers could possibly increase yield. The objective of this research was to compare peg strength of three peanut cultivars with peanut maturity (mesocarp color), pod yield and pod loss over three planting dates and four harvest dates per planting date. The land was prepared using normal planting procedures. The crop was irrigated using IrrigatorPro for peanut verified using soil water potential sensor measurements. Peanut was planted at three planting dates, early, on time and late at two week intervals. At harvest 4-5 plants were hand harvested, washed and excess peanut vine and leaves were removed from only two of the plants leaving only a small portion of the stem with the attached peg and peanut. Peanuts were place in a “u-shaped” metal bracket that was attached an electronic force gage (Imada, Inc. Model DS2-11, Northbrook, IL, that would measure peak force required to detach the peg from the peanut. After each peanut was detached from the peg, the peanut was placed in an individual numbered pvc cell to correlate peg strength with hull color. When all the peanuts from the two plants were placed in the pvc grid, another screened plate with a wood frame was placed on top as a lid and held in place with elastic bungee cords. The peanuts were then blasted using a pressure washer similar to when peanuts are prepared for the hull scrape method. Peanut yield was determined using normal procedures. An experimental peanut scavenger designed and built at the National Peanut Research Laboratory (Dawson, Ga) was used to collect pod loss. Peg strength was correlated with pod yield, pod loss, and with individual peanut pod color. Peg strength, pod yield, and pod loss decreased values with each harvest date. Peg strength and pod yield were not different for harvest 1 and 2 but did show difference for harvest 3 and 4. Pod loss increased with each harvest date. Average peg strength by cultivar showed all three cultivars different from each other with Ga-O6G having the greatest peg strength followed by Ga-O9B and then Tifguard. There was no relationship between peg strength and pod maturity for the cultivars tested. Peg strengths were different for each cultivar with plant date and harvest date. Thus, peg strength could be used as a breeding metric for cultivar selection. There was no relationship between peg strength and peanut maturity. Therefore, the use of peg strength as a method to determine peanut m

Technical Abstract: Mesocarp hull color is the current standard to estimate digging date and peanut maturity. The objective was to determine if peg strength could be used to predict peanut maturity instead of hull color. Peanut peg strength was collected on three peanut cultivars (Ga-O6G, Ga-O9B, and Tifguard), planted at three dates, and harvested at four dates to determine the relationship between peg strength and pod maturity. Average peg strength was different for all three cultivars with Ga-O6G having the greatest average peg strength followed by Ga-O9B, and Tifguard. There was not a linear relationship between peg strength and pod maturity (R2=0.007). The non-relationship between peg strength and maturity implies peg strength was not a valid criteria to determine pod maturity or predict digging date. Overall, peg strength may be useful to describe cultivar characteristics during the breeding process but may not be sufficiently robust enough to predict digging date.